Process for soil improvement

ABSTRACT

A process for improving clayey soils for cultivation consisting essentially of incorporating a carbonate of calcium into clayey soils and inducing a gas formation in said soils by chemical reaction by an acidic treatment of said soil with an acidic material containing a silicon compound, in approximately stoichiometric amounts based on the carbon dioxide content of said carbonate of calcium, whereby porous aggregates are built up.

United States Patent [191 Zimmermann et al.

[ Dec. 17, 1974 PROCESS FOR SOIL IMPROVEMENT Filed: Feb. 29, 1972 Appl. No.: 230,495

130] Foreign Application Priority Data Sept. 13. 1968 Austria A 8947 Related U.S. Application Data [63] Continuation-impart of Ser. No. 858,910, Sept. 12,

1969, abandoned.

[52] U.S. Cl. 47/58, 47/DIG. 10 [51] Int. Cl A0lb 79/02 [58] Field of Search 47/58, DlG. 10; 71/1 [56] References Cited I UNITED STATES PATENTS 1,667,923 5/1928 Bishop 47/58 X 2,702,966 3/1955 Boyd 47/58 2,741,876 4/1956 Paoloni. 47/58 2,773,330 12/1956 Erwin.... 47/58 2,799,973 7/1957 Smith 47/58 2,816,396 12/1957 Ross et a1. 47/58 2,816,397 12/1957 Becker 47/58 3,337,989 8/1967 Harmon 47/58 Primary ExaminerRobert E. Pulfrey Assistant ExaminerE. M. Coven Attorney, Agent, or FirmHamm0nd & Littell [57] ABSTRACT A process for improving clayey soils for cultivation consisting essentially of incorporating a carbonate of calcium into clayey soils and inducing a gas formation in said soils by chemical reaction by an acidic treatment of said soil with an acidic material containing a silicon compound, in approximately stoichiometric amounts based on the carbon dioxide content of said carbonate of calcium, whereby porous aggregates are built up.

5 Claims, No Drawings PROCESS FOR SOIL IMPROVEMENT REFERENCE TO A PRIOR APPLICATION This application is a continuation-in-part of our copending US patent application Ser. No. 858,910 filed Sept. 12, 1969 and now abandoned.

THE PRIOR ART It is known that soils which developed from carbonaceous sediments, on agricultural usage over particu larly long periods of time, have a good structure which is not only characterized by a natural bonding of the clayey coagulate in stable aggregates but also by their porosity. The best example for this are the younger carbonaceous loess soils whose stable crumbs result in a particularly good hydrodynamic and plant nutrition dynamic of the soil. Contrary to this, many heavy clay soils with a high clay content which have been leached, and clay-rich sloping virgin soils on medium altitude mountains have no useful structure. The clayey particles of the aged cultivated surface soils as well as the clayey particles of the mountains virgin soils, produced by weathering, have a strong tendency to mud formation.

It has already been suggested, to incorporate calcium carbonate in soils together with substances, which liberate carbon dioxide. Particularly, acid-producing bacteria have been suggested for this. It has also been attempted to improve soils by the addition of silicates, particularly potassium silicates. The densely seated particles are dispersed thereby, and an increase of the pore volume is attained. However a stability of the crumbs of the thus treated soil is not effected by this treatment. Also in this process, which works without gas evolution, no loosening of the soil is effected.

OBJECTS OF THE INVENTION An object of the invention is to improve so-called heavy cultivated'soils and clay-rich virgin soils by the production of porous aggregates through addition of gas-producing chemicals to the soils.

Another object of the invention is the development of a process for improving clayey soils for cultivation consisting essentially of incorporating from to 750 gm/m of a carbonate of calcium into clayey soils and inducing a gas formation in said soils by chemical reaction by an acidic treatment of said soil with an acidic material selected from the group consisting of acidic silica sols, acid-adjusted alkali metal silicate suspensions and mixtures of alkali metal silicates and acidic calcium phosphates, in approximately the stoichiometric amount based on the carbon dioxide content of said carbonate, whereby porous aggregates are built up.

These and other objects of the invention will become more apparent as the description thereof proceeds.

DESCRIPTION OF THE INVENTION Suitable carbonates of calcium which decompose under acidic treatment with formation of carbon dioxide are calcium carbonate, if necessary, in the form of carbonaceous rocks, or double carbonates such as dolomite. The addition of these products is done in a finely ground state, preferably by thoroughly mixing and incorporating into the top layer of soil, such as by rototilling. The amount depends upon the quality of the soil, and amounts generally between 20 to 750 gmlm are incorporated into the soil.

The gas formation can be induced by further addition and incorporation of acidic silicon-containing compounds in solid or liquid form to the soil.

The special realization of the process consists in adding to the soil, as acidic silicon-containing substances, acidic silica sols and/or acidic-adjusted alkali metal silicate suspensions and/or mixtures of alkali metal silicates and acidic calcium phosphates to induce CO gas formation. The acidic-adjustment of the silica sols and the silicate suspensions is suitably done with phosphoric acid. In principle, however, any acidic substance can be used, such as other inorganic acids such as sulfuric acid or hydrochloric acid or organic acids capable of giving the desired pH range. It is, however, appropriate to use such products which for other reasons are favorable for the structure and the nutritional content of the soil, as phosphoric acid or the acidic phosphates, preferably acid calcium phosphates (superphosphates and triplephosphates). Appropriately, approximately stoichiometric amounts based on the CO content of the carbonate utilized are used. The reaction between these compounds starts relatively quickly in the soil, particularly if the latter is moist. The acidic siliconcontaining substances can, however, also be added to the soil in liquid form, e.g., by spraying.

In using the acid-adjusted silicate suspensions it is appropriate to work with high dilutions, as, for example, from 3 to 10 percent solutions, in order to avoid agglomeration, or, respectively, to prepare the suspensions only immediately before use. For this purpose alkali metal silicates such as potassium and sodium silicates can be used. The mol ratio of alkali oxide to SiO can vary to a large extent in these silicates. Preferably, commercial products in a mol ratio of from 1:2 to 1:6 are used. A certain stabilization of the alkali metal silicate solutions can be obtained by an addition of urea in amounts of from 1 to 5 percent, based on the solid content of the alkali metal silicates.

In so far as acidic silica sols and/or acidic adjusted silicate suspensions are used, the appropriate pH range is between 2 and 5.

The acid treatment with acidic silicon-containing substances can also be conducted by adding to the carbonate of calcium treated soil a solid mixture of an al' kali metal silicate and an acidic calcium phosphate. Such a treatment is preferable in the spring when an ample supply of water is assured to effect the solution and chemical reaction of the reactants to give a carbon dioxide gas evolution.

It has been proven advantageous, particularly if the separate components are not added in solid form, to bring about an increased effect of the gas formation on the soil particles by soil tilling. Through the volume increasing effect of the gas phase, a build-up of porous aggregates is accomplished, not only in cultivated soils whose aggregates break down easily, but also in virgin soils with high clay content.

The following examples are illustrative of the practice of the invention without, however, being limitative in any respect.

EXAMPLE I On a test field with muddy clay soil, deficient in lime, the arable soil shows slate-like and coherent sttuctures. Less than percent of the soil volume are coarse pores 10p.). After the expansion due to frost, the soil easily gets muddy and moist. The taking up of moisture leads to a quick stopping of any biological activity. A regulated gas exchange with the atmosphere, which is indispensable not only for the soil life but also for the root breathing of plants, becomes impossible due to the lack of capillary pores. The consequence of such unfavorable physical and biological conditions in this soil is the stunting of germinating grain and the loss of two to four crops in a crop rotation of 5 years.

To create a normal crumb structure the following steps were taken:

erwise would run off without penetrating into the soil.

Into the pulverized virgin soil were then worked in together, for each running meter of the ditches, 100 gm of finely ground chalk, previously mixed with 80 gm of air-dried, powdery alkali metal silicate hydrate (solid content, 65 wt percent of SiO ,l9.4 wt percent of Na O, mol ratio SiO :Na 0=3.35:1) and 100 gm of triple phosphate. Since thesoil was moist at the start of At the end of March, after the finish of the frost period and the drying off of the field, 6,000 kg/hectare of finely ground limestone were thoroughly incorporated into the top horizontal layer of 7 m8 cm depth.

In the second and third operations, two tractors followed in immediate succession. The first one sprayed a dilute aqueous acidic silicate suspension from a plantprotective spraying apparatus. The second one thoroughly incorporated the frothing reaction mass of soil particles, limestone, and acidic silicate suspension to a depth of approximately 8 cm.

This treatment lead to an 8 cm layer, crumbly throughout, which is sufficient to secure the strong germination and the root growth of the spring wheat plants, until they are strong enough to grow through the denser, deeper layer. On a matching field with equal cultivation and equal lime application but without acidic treatment, the young absorbent roots of the grain seeds died after warping and yellowing in a depth of from 4 to 7 cm, so that the sowing was fruitless.

The spraying acidic silicate suspension had the following composition:

The growth on the test lots proceeded normally while the untreated lot had to be ploughed up.

EXAMPLE II On a mountain slope adjacent to a viniculture the slight, weathered layer on a gypsum Keuper is so clayey that only weeds which can endure a strong lack of air in the soil can thrive. The sloping lot was prepared and made suitable for viniculture.

To this purpose the following steps were taken:

First, in a local restriction of the operation three ditches, similar to drainage ditches with vertical walls, were filled with treated soil. The ditches were made in the direction and in the distance of the vines to be planted; two of them serve for the planting of the seedlings, the middle ditch, situated between them, serves to conserve for the run off of the rain water, which oththe work in early spring, the reaction between the calcium carbonate and the acidic calcium phosphate began quickly. The soil crumbs formed are largely water stable and yield optimum water-air exchange in the 10 cm wide and 16 cm deep ditches which were filled with the treated soil. The young vines grow well on the technically created location. Excess rain water is conserved and run off through the soil-drainage line passing through the middle of the interspace between the rows of vines.

EXAMPLE III COMPARATIVE TESTS OF SOIL IMPROVEMENT By the process of the invention, clayey soils were improved by working into the soil calcium carbonate together with an acidic material from the group a. acid-adjusted acidic silica sol b. acid-adjusted alkali metal silicate suspensions c. mixtures of alkali metal silicates and acidic calcium phosphates (commercial Triple Phosphate" P O content 48 percent) Calcium carbonate and the acidic materials were applied in approximately stoichiometric amounts.

The below listed tests have the purpose of showing that through the above described process a quite considerable improvement of the soil occurs, that can be made visible by an aggregation of the soil particles.

A. Experimental (Analysis of sieving and of aggregates) The percentage of aggregates, not larger than 0.2 mm in clayey soils was determined by the method of Tjulin, improved by-Meyer and Rennenkampf, as developed by the Technische Hochschule, Braunschweig, Germany.

According to this method, the air-dried soil, treated each time in the listed manner, or also untreated, is crushed mechanically. Subsequently the particles whose diameter is l 8 mm are screened off and slightly moistened with water or with a solution containing the additions, to be examined.

The thus pre-treated aggregates are subjected to disintegration by several dippings in water in a pendulum apparatus. Subsequently a screening of the aggregates over 0.2 mm is carried out.

, The results are thereby compared with untreated aggregates (no additives) as well as with aggregates that are obtained, if a potassium silicate solution or if calcium carbonate and acidic calcium phosphate are used. In this connection it is pointed out that the combination of calcium carbonate and acidic calcium phosphate for soil treatment is, in itself, not previously known.

The numerical values listed in the following tables are in each case average values that were obtained on the basis of several tests, carried out successively with the same soils under the same conditions. In the following Table I the results in the left column are with the untreated sample, the results in the center column are with calcium carbonate and acidic phosphate, and the percentage of the particles above 0.2 mm determined. results in the right column are with calcium carbonate The results are reproduced in Table II.

and acidic silica sol (a), or acid-adjusted alkali-metal TABLE H silicate suspensions (b), or a mixture of alkali-metal silicate and acidic calcium phosphate all in approxi- Type of so share in of Over 02 mm mately stoichiometric amounts. The acid utilized for Untreated Potassium Silicate Solution the acid-adjustment of (a) and (b) was phosphoric B 175 [9 acid. The resultant solutions had a pH of about 3. In the C 12.1 13.9

following Table II, the results in the left column are with the untreated sample and the results in the right column are with a soil treated with a potassium silicate solution.

In the test series A a humus containing clayey soil was used. In the test series B the tests were carried out 0 C. Discussion of the Results The numerical values, listed in the right column of the Table I, for percentage of the aggregates, show clearly that an improved aggregate formation is obtained if calcium carbonate and the listed acidic matewith a clayey virgin soil (mountain clay), wh in the rials are added to the various clayey soils. These results test series C a clayey salt containing mud was used. are surprisingly particularly good if aeichadjusted For each test Series m the dlfferem 5011s calclum acidic silica sol (cf. test series a) or acid-adjusted albonate in an amount of 100 gin/m2 were worked in kali-metal silicate suspensions (cf. test series b) or mix- P of working-in 8 and Subsequently the Soil tures of alkali-metal silicates and acidic calcium phoswas treated with a solution or suspension of the above 2 h t 1 t t Series are k d i t th il, Th named acidic materials- A5 a further Control test, a control tests utilizing untreated soils, aswell asthe tests treatment of the soils with calcium carbonate and that were conducted with calcium carbonate and acidacidic calcium phosphates was carried out. Also as a adjusted phosphates, as in Table I, or the tests that were further control test, a treatment with a potassium siliconducted with a corresponding amount of a potassium cate solution'was carried out. The amount of the va isilicate solution, as in Table I], make it clear, that a parous acidic agents, that were supplied in this way to the tieularly unexpected yh 'g e increase Occurs: in the soils was in a stoichiometric proporation to the worked above described tests, If he 8011s are treated with ea]- in amounts 0f calcium carbonate Then the Soils were cium carbonate and one of the acidic silicon-containing left alone for some time and subsequently the aggregate agents f mventlon 9 (1), (b) or f ti was examined by the above described In addition, as shown in Example I, treatment of the method of Tjulin. Each time one sample was left un- .501] Mm calclilm a? alone does lead to any treated for comparison. The single test series were re- Improvement m S011 condltlons of clayey sons The ventional silicate compounds suggested for the treatgszigg sgfiz m Order to be able to determme ment of clayey soils are alkaline or only very weakly 3 5 acidic, such as silica sols. A solution of silicic acid (sil- Results ica sol) is an exceptionally weak acid, weaker than car- The results with the various treated or untreated solls bonic acid and would not liberate carbon dioxide from and the various acidic materials that were used in coma Calcium carbonate bination with calcium carbonate, are listed in the fol- The preceding Specific embodiments are illustrative lowing table- The different y y Soils, designated with 4 of the practice of the invention. It is to be understood, A, B and C were already mor e Closely explained in the however, that other expedients known to those skilled experimental part. The various figures give the percenti h t may b l d ith t d ti f th age of aggregates that are larger than 0.2 mm. The left irit f th inv ntion. column gives the results with the untreated soil while We claim: in the center column the results are given that were obl. A process for improving clayey soils for cultivation tained in a treatment with calcium carbonate and consisting essentially of incorporating from 20 to 750 acidic phosphate. Finally, in the right column the regm/m? of a carbonate of calcium into clayey soils and suits are listed that were obtained by the addition of mducmg a gas f rmat n in said soils by chemical reaccalcium carbonate in combination with acidic material, y an acidic treatment of Said h all i i namely material selected from the group consisting of acidic iddj d idi silica silica sols, acid-adjusted sodium silicates spensions b. acid-adjusted alkali-metal silicate suspensions and mlxtures sodlumelheates and aelfillc f fl t'fl c. mixtures of alkali-metal silicates and acidic calphosphates approxlmatellf h stelehlemetffc cium phosphates in the listed sequence amount based on the carbon dioxide content of said carbonate, whereby porous aggregates are built up.

TA I I 2. The process of claim 1 wherein said acidic material contains phosphoric acid. Type of Share in of over 0.2 mm 3. The process of claim 1 wherein said acidic material has a pH of between 2 and 5.

Untreated Amdlc phosphate 4. The process of claim 1 wherein said gas formation czico CaCo, 0 1S brought to an increased effect on said soil by 8011 tilling. 12 21:; 22:2 5. The process of claim 1 wherein said gas formation c 12.1 31.3 43.4 (c) in said soils is induced by incorporation into said soil of a solid mixture of sodium silicates and acidic calcium phosphates capable of reacting with said carbonate of In a further test, the soils of the types B and C e calcium in the presence of moisture to induce said gas treated by the described method of Tjulin with a correformation.

sponding amount of potassium silicate solution and the UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 385424l Dated December 1974 Friedrich Zimmermann et al.

Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' [73] Assignee: Henkel G Cie GmbH, Dusseldorf, Germany Column 3, line 7, "sttuctures" should read structures Signed and Sealed-this eleventh OF November 1975 {SEAL} Arrest:

O RUTH c. MASON c. MA-RSHALL DANN .-ll!('slillg Officer ('mnmissimur nj'larents and Trademarks FORM PO-1050 (10-69) uscoMM-Dc scan-P09 U,S GOVERNMENT PRINTING OFFICE 1 869- 9 

1. A PROCESS FOR IMPROVING CLAYEY SOILS FOR CULTIVATION CONSISTING ESSENTIALLY OF INCORPORATING FROM 20 TO 570 GM/M2 OF A CARBONATE OF CALCIUM INTO CLAYEY SOILS AND INDUCING A GAS FORMATION IN SAID SOLIDS BY CHEMICAL REACTION BY AN ACIDIC TREATMENT OF SAID SOIL WITH AN ACIDIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF ACIDIC SILICA SOLS, ACID-ADJUSTED SODIUM SILICATE SUSPENSIONS AND MIXTURES OF SODIUM SILICATES AND ACIDIC CALCUIM PHOSPHATES, IN APPROXIMATELY THE STOICHIOMETRIC AMOUNT BASED ON THE CARBON DIOXIDE CONTENT OF SAID CARBONATE, WHEREBY POROUS AGGREGATES ARE BUILT UP.
 2. The process of claim 1 wherein said acidic material contains phosphoric acid.
 3. The process of claim 1 wherein said acidic material has a pH of between 2 and
 5. 4. The process of claim 1 wherein said gas formation is brought to an increased effect on said soil by soil tilling.
 5. The process of claim 1 wherein said gas formation in said soils is induced by incorporation into said soil of a solid mixture of sodium silicates and acidic calcium phosphates capable of reacting with said carbonate of calcium in the presence of moisture to induce said gas formation. 